Callie (Sara Ramirez) breaks the news to Mark (Eric Dane) that she is pregnant with his child ... and at first the "Grey's Anatomy" plastic surgeon and well-documented player is delighted.
"Are you kidding?" he says. "That is my kid in there. I am a dad. We are parents of a baby. Should we get married?"
To which a much cooler head prevails when Callie replies, "Oh, no. I am all for raising a baby with you, but there is a line."
The reality sets in and Mark realizes he has to break the news to his lady love.
"That is good because I am in love with Lexie [Chyler Leigh]. …And oh, God . What am I going to tell Lexie?" he wonders.
While Mark is trying to figure that out, Callie is driving her new obstetrician (Rachael Taylor) crazy, and Arizona (Jessica Capshaw), Mark and Callie have to figure out how to deal with the unexpected baby business.
Also on tonight's episode, Derek (Patrick Dempsey) begins work on his Alzheimer's clinical trial, and Miranda Bailey's (Chandra Wilson) OR tweet fest gets a cold reception from the Chief (James Pickens Jr.).
"Grey's Anatomy" airs Thursdays at 9 p.m. on ABC.